Voice processing is used in many modern electronic devices, including, without limitation, mobile telephones, headsets, tablet computers, home theatre, electronic games, streaming, and so forth.
Harmonicity of a signal is a measure of the degree of acoustic periodicity, e.g., expressed as a deviation of the spectrum of the signal from a perfectly harmonic spectrum. A measure of harmonicity at a particular time or for a block of samples of an audio signal representing a segment of time of the audio signal is a useful feature for the detection of voice activity and for other aspects of voice processing. While not all speech is harmonic or periodic, e.g., sections of unvoiced phonemes are articulated without the vibration of the vocal cords, the presence of at least some harmonic content is an indicator of vocal communication in most languages. In contrast, many undesirable audio signals other than voice, e.g., noise are inharmonic in that they do not contain harmonic components. Hence, a measure of harmonicity is particularly useful as a feature indicative of the presence of voice.
One measure of harmonicity is the Harmonics-to-Noise Ratio (HNR). Another is the Subharmonic-to-Harmonic Ratio (SHR).